replace some points with vectors to clarify documentation

Some SkIPoint and SkPoint methods become clearer if their
parameters or return value is typed as a vector.

Since SkPoint is identical to SkVector (and SkIPoint is
identical to newly added SkIVector) this has no impact
on compiled code.

Some routines arguably have multiple possible point and
vector combinations which will be included in eventual
documentation; the interface should have the most common
and/or logical choice.

Some of my choices could be argued with as well. Does
SkPoint::Normalize take a SkPoint? Afternative points
of view encouraged.

R=reed@google.com,bsalomon@google.com
Bug: skia:6898
Change-Id: I2429b9d43b20351188d7c6433620a2e221f75bd8
Reviewed-on: https://skia-review.googlesource.com/69680
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Cary Clark <caryclark@skia.org>
1 file changed